1. Field of the Invention
The subject invention generally relates to an apparatus that is equipped to remove unreacted isocyanate from a gaseous waste stream and a method of removing the isocyanate from the gaseous waste stream. More specifically, the subject invention relates to an apparatus that has a medium for removing the unreacted isocyanate from the gaseous waste stream.
2. Description of the Related Art
Many processes involve the use of isocyanate. One of the most prevalent processes that involves the use of isocyanate is the production of polyurethane. For the production of polyurethane, an apparatus is provided that includes a mold for receiving a composition that includes the isocyanate. In addition to the isocyanate, the composition includes another component that is reactive with the isocyanate component, such as a polyol or polyamine, to form the polyurethane. One of the problems in the production of polyurethane from the composition including the isocyanate is that unreacted isocyanate is a highly volatile chemical and readily vaporizes from the composition. The EPA has environmental regulations that stipulate a rate at which isocyanate can be released into ambient atmosphere. For this reason, the unreacted isocyanate that has vaporized from the composition is typically contained within an area around the mold in the apparatus to prevent the unreacted isocyanate from escaping into the ambient atmosphere. The unreacted isocyanate is gathered as part of a gaseous waste stream. The unreacted isocyanate, among other components, is removed from the gaseous waste stream with a medium before the gaseous waste stream is discharged into the ambient atmosphere.
A typical medium that is used for removing the unreacted isocyanate from the gaseous waste stream is an activated carbon bed. Activated carbon beds are effective for removing the unreacted isocyanate from the gaseous waste stream; however, the activated carbon beds have many disadvantages. For example, activated carbon beds function by adsorbing the gaseous waste stream, with components in the gaseous waste stream sticking to the activated carbon. To adsorb the gaseous waste stream, the gaseous waste stream is forced through the activated carbon bed, which provides a porous matrix, at high pressure. A pressure drop across the activated carbon bed is often substantial, i.e., pressure drops of about 12 inches of water column are not uncommon. Higher pressure drop correlates to increased cost of producing the polyurethane since excessive amounts of energy are required to force the gaseous waste stream through the activated carbon bed. Furthermore, the activated carbon beds are extremely heavy and bulky, which limits process design. The activated carbon beds are also difficult to operate and require extensive maintenance. Other media used to remove the unreacted isocyanate and the other components have similar drawbacks.
Due to the deficiencies of the current media used to remove unreacted isocyanate from the gaseous waste stream, there remains an opportunity to provide an apparatus including a medium and a method of removing unreacted isocyanate from a gaseous waste stream without the drawbacks of the activated carbon bed in order to allow for greater flexibility in process design. There is also an opportunity to provide an apparatus including a media and a method of removing unreacted isocyanate from a gaseous waste stream that is easier to operate and that does not require extensive maintenance, as compared to the current media used to remove unreacted isocyanate from gaseous waste streams. Further, there is an opportunity to provide an apparatus including a medium and a method of removing the isocyanate from the gaseous waste stream that exhibits a lower pressure drop than currently achieved with the activated carbon beds to improve process efficiency and reduce energy that is required to force the gaseous waste stream through the medium, while removing comparable amounts of the unreacted isocyanate from the gaseous waste stream.